A pair of photons that traveled 7.3 billion light-years in space arrived at NASA's Fermi Satellite Space Telescope, nine-tenths of a second apart. The energy of one photon is a million times the energy of the other, which gives confirmation to Einstein's special theory of relativity.
A pair of photons that traveled 7.3 billion light-years in space arrived at NASA's Fermi Satellite Space Telescope, nine-tenths of a second apart. The energy of one photon is a million times the energy of the other, which gives confirmation to Einstein's special theory of relativity.
The Einsteinian view of the structure of space-time predicts that every electromagnetic wave - gamma rays, radio, infrared, visible light and X-rays - will travel through space at the same speed, regardless of the energy it has. But in some of the new gravity theories (ie quantum gravity theories), space-time is not continuous but has the texture of foam, when looking at scales a trillion times smaller than the electron. These theories predict that the fabric of space-time will slow down high-energy gamma-ray photons more than low-energy ones. This clearly did not happen here.
Even in the world of energetic particles, where every difference of a second is meaningful, the difference of nine tenths of a second when talking about a distance that spans 7 billion light years, is so small that it is more likely to be due to the process of the burst of gamma radiation than to confirm Einstein's ideas .
"These measurements rule out any approach to a new theory of gravity that predicts a change in the speed of light as a function of the amount of energy," says Peter Michelson, professor of physics at Stanford University, and director of research at the Fermi Institute (LAT), which located the pair of photons.
Michelson's paper is described in detail in the journal Nature, October.
Physicists have longed for years for a unified theory that would describe how the universe works. But no one has yet come up with one that unites all four fundamental forces of nature. The standard model, which reached its latest version in the late 70s, unifies only three of the four forces: electromagnetism, the strong nuclear force, and the weak force. Gravitation has never fit the models and although scientists are working on developments for new theories, no breakthrough has yet been made in the field.
Einstein's theories of relativity also fail to answer this problem.
"Physicists want to replace Einstein's point of view on gravity - as it is reflected in the theories of relativity - with something that can deal with all the fundamental forces," says Michelson. "There are many ideas, but few ways to test them".
The two photons provided rare empirical evidence regarding the structure of spacetime. But it is not yet known whether the testimony will settle the disputes or not.
The photons embarked on the galactic marathon during a massive gamma-ray burst apparently caused by the collision of two neutron stars, the most dense objects known to us.
A neutron star is formed when a massive star collapses in on itself in a supernova explosion. It forms inside the core when material with a mass exceeding that of our Sun is compressed to a diameter of only 16 kilometers. When two such compact objects collide, the energy released causes a burst of gamma rays and can reach a brightness a million times greater than the entire Milky Way galaxy, for a short time. The burst (GRB 090510) that sent out the two photons lasted only 2.1 seconds.
NASA's Fermi Satellite Space Telescope is a collaboration in astrophysics and particle physics, developed together with the US Department of Energy (DOE) and academic institutions in France, Germany, Italy, Japan, Sweden and the USA.
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point:
Is it physical to talk about the past?
We cannot reach it either (unless we go beyond the speed of light) and it is even more likely to claim that it no longer exists.
The future probably doesn't exist yet either.
In short - the restrictions you are trying to introduce will prevent, if implemented - any meaningful discussion on any topic.
beyond everyday use,
Does the word "now" have a physical meaning in the context of distances we can never reach?
To measure distance a ruler must be stretched between 2 points.
Although it is true that you can say "suppose we stop everything and quickly reach from here to the second point we want to measure", but it must be remembered that the theory of relativity forbids flying above the speed of light.
That is, it is not impossible that the point that is "now" at a distance X no longer exists. So what does it mean when we say "the distance to that point".
In short, it seems to me that it is not physical to say "now" about those distant points.
Read here:
http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN
the following explanation:
If the Universe is only 14 billion years old, how can we see objects that are now 47 billion light years away?
When talking about the distance of a moving object, we mean the spatial separation NOW, with the positions of both objects specified at the current time. In an expanding Universe this distance NOW is greater than the speed of light times the light travel time due to the increase of separations between objects as the Universe expands. This is not due to any change in the units of space and time, but just caused by things being farther apart now than they used to be.
What is the distance NOW to the most distant thing we can see? Let's take the age of the Universe to be 14 billion years. In that time light travels 14 billion light years, and some people stop here. But the distance has grown since the light traveled. The average time when the light was traveling was 7 billion years ago. For the critical density case, the scale factor for the Universe goes like the 2/3 power of the time since the Big Bang, so the Universe has grown by a factor of 22/3 = 1.59 since the midpoint of the light's trip. But the size of the Universe changes continuously, so we should divide the light's trip into short intervals. First take two intervals: 7 billion years at an average time 10.5 billion years after the Big Bang, which gives 7 billion light years that have grown by a factor of 1/(0.75)2/3 = 1.21, plus another 7 billion light years at an average time 3.5 billion years after the Big Bang, which has grown by a factor of 42/3 = 2.52. Thus with 1 interval we got 1.59*14 = 22.3 billion light years, while with two intervals we get 7*(1.21+2.52) = 26.1 billion light years. With 8192 intervals we get 41 billion light years. In the limit of very many time intervals we get 42 billion light years. With calculus this entire paragraph reduces to this.
Another way of seeing this is to consider a photon and a galaxy 42 billion light years away from us now, 14 billion years after the Big Bang. The distance of this photon satisfies D = 3ct. If we wait for 0.1 billion years, the Universe will grow by a factor of (14.1/14)2/3 = 1.0048, so the galaxy will be 1.0048*42 = 42.2 billion light years away. But the light will have traveled 0.1 billion light years further than the galaxy because it moves at the speed of light relative to the matter in its vicinity and will thus be at D = 42.3 billion light years, so D = 3ct is still satisfied.
If the Universe does not have the critical density then the distance is different, and for the low densities that are more likely the distance NOW to the most distant object we can see is bigger than 3 times the speed of light times the age of the Universe. The current best fit model which has an accelerating expansion gives a maximum distance we can see of 47 billion light years.
In this article:
http://www.space.com/scienceastronomy/mystery_monday_040524.html
Write:
All the pieces add up to 78 billion-light-years. The light has not traveled that far, but "the starting point of a photon reaching us today after traveling for 13.7 billion years is now 78 billion light-years away," Cornish said. That would be the radius of the universe, and twice that — 156 billion light-years — is the diameter. That's based on a view going 90 percent of the way back in time, so it might be slightly larger.
The same text also appears here:
http://www.msnbc.msn.com/id/5051818/
And here:
http://news.bbc.co.uk/2/hi/science/nature/3753115.stm
And if you read here:
http://en.wikipedia.org/wiki/Size_of_the_universe
Among other things, we find that:
The age of the Universe is about 13.7 billion years, but due to the expansion of space we are now observing objects that are now considerably farther away than a static 13.7 billion light-years distance. The edge of the observable universe is now located about 46.5 billion light-years away
Hubble's idea about the redshift is correct, but only on average. And of course it cannot be assumed about a single object and theories can be built on it. You can think of a star that is relatively close and that happened to accelerate rapidly towards a black hole and then explode, we will get the same red shift...
http://www.cbc.ca/health/story/2006/03/16/cosmos-expands060316.html
http://www.astronomycafe.net/qadir/ask/a11167.html
Obviously a flux of photons of all kinds of energies was emitted, but 2 photons (with energy differences) are enough to confirm the claim.
How do you know the distance - as I said, you know it by red shift.
The more distant a galaxy is from us, the greater its velocity and the higher its redshift. By differential calculation, it is possible to deduce where the object we are looking at is located.
When you do the calculation, you conclude where the galaxy is today and not at the moment when the photons were sent, otherwise for the galaxies at the edge of the universe, you have to get a very close distance calculation, because these are galaxies that existed with the formation of the universe (about a million years after the bang) and you have to get a calculation that gives a terrible distance Very short, because a million years after the bang all the galaxies were still dense and clustered together.
Eddie:
I don't understand what you are saying.
Gamma photons were absorbed.
Gamma photons are usually emitted for only a few seconds and in extreme cases for an hour.
It has nothing to do with Short.
Short is a subclass within the GRB and the various definitions (like Afterglow) also apply to it.
What is the issue here at all - other than your attempt to say that you understand the research better than those who conducted it?
Michael Rothschild,
The issue under the title Short gamma-ray bursts is specific compared to the general opening starting with - Gamma-ray bursts (GRBs.
The more specific issue is the exact and relevant one to our case (the claim regarding a radiation outburst due to the collision of two neutron stars). That's why I only referred to her in the quote.
Regarding the scenario of the union of two neutron stars - it seems certain that you are right.
Eddie:
Regarding response 24 - this is true, but you forgot to mention what else is written - in the fourth sentence in the first paragraph of the link:
The initial burst is usually followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio).
Regarding the scenario of the union of two neutron stars, the scenario described by Ehud seems correct to me with the addition of one note: if the current predictions of relativity are correct then some of the gravitational energy will also be released as gravitational waves.
This is of course what will also happen when two black holes merge.
sympathetic,
The speculation makes sense.
It is possible to imagine that two neutron stars approach each other and enter into an increasingly accelerating rotational dance around each other, ideal for the 'frictional' collision - that is, at a relatively small angle. Only sophisticated mathematics can determine if there is any particular type of case where gravitational forces will exceed kinetic forces.
By the way, is it possible for a situation where after a powerful frictional encounter - the two objects (wounded and bleeding electrons to a certain extent) will repel each other with the force of kinetic energy (as happens, let's say, in an encounter between an aircraft like Columbia and the atmosphere, if the encounter is at a certain speed and at a certain angle)?
Michael Rothschild and Ehud,
From the link provided on the 18th:
Events with a duration of less than about two seconds are classified as short gamma-ray bursts. Until 2005, no afterglow had been successfully detected from any short event and little was known about their origins. Since then, several dozen short gamma-ray burst afterglows have been detected and localized, several of which are associated with regions of little or no star formation, including large elliptical galaxies and the intracluster medium.[38][39][40] This rules out an association with massive stars, confirming that short events are physically distinct from long events. The true nature of these objects (or even whether the current classification scheme is accurate) remains unknown, although the leading hypothesis is that they originate from the mergers of binary neutron stars.[41] A small fraction of short gamma-ray bursts are probably associated with giant flares from soft gamma repeaters in nearby galaxies.[42][43]
According to the article - the explosion (GRB 090510) that sent the two photons lasted 2.1 seconds. If the gamma-ray burst continued throughout this time - then the matter is borderline, and it is possible that this is a normal supernova event. It's a shame the article isn't more detailed...
They swallowed, they didn't swallow.
Eddie
Allow me to make several speculations about which I have no reliable knowledge:
The energy obtained from the collision of two neutron stars is their kinetic and gravitational energy
Because of their enormous mass the two sources of energy mentioned above are huge. What is clear is that the excess energy as a result of the explosion is released in gamma radiation. What happens after the explosion (again purely speculation)
If they have enough mass to produce a black hole then one will form. If the mass of both is insufficient
They will merge into one neutron star. Since a neutron star consists of degenerate neutrons (almost all states below the Fermi level are full) it will be necessary to produce a new Fermi level and in this process energy will be released.
Michael Rothschild and Ehud - both of you together and one separately - thank you.
"The photons embarked on the galactic marathon during a massive gamma-ray burst that was probably caused by the collision of two neutron stars, the most dense objects known to us."
From this I understand that the supernova from which the two photons came out was 'probably' created by the collision of metron stars.
I don't know what led to this hypothesis, but I suppose there is a reason for the Chorus to think that it is indeed so.
As for myself, it is not clear to me what happens when two neutron stars 'collide'. If it's black guys - then it's clear that they are swallowed by each other. If it is white dwarfs - there will be a supernova here (I have no idea what happens in the collision of two quark stars, assuming such stars exist).
The escape velocity from a neutron star is over half c. On the other hand, the star itself does not continue to collapse after becoming neutrons, just because of Pauli's prohibition principle. So what really happens in the collision of two neutron stars?
Do they in any case necessarily 'explode' i.e. cease to be neutron stars, or is there a certain possibility that they will stick together due to the enormous force of gravity, and even if there are no more neutron stars they will become a white dwarf? Or because of the increased mass at a small radius they collapse and form a black hole?
In the article, the source of the photons is specified as GRB 090510, where GRB stands for Gamma Ray Bursts (which, by the way, an important step in their understanding was achieved by a pair of astrophysicists from the Hebrew University, Zvi Piren, who was his doctoral student at the time and is now a professor in his own right, Ram Sri). The source of the gamma pulses is either a supernova or a collision between neutron stars.
Eddie:
Here is a more complete description:
http://en.wikipedia.org/wiki/Gamma-ray_burst
Assume that the researchers knew how long the gamma ray burst lasted in the case before us, if only because they watched it.
In the alternative assumptions to the theory of relativity, it is very improbable that the radiation was created in order and with such time differences that caused all the frequencies to reach the earth at exactly the same second.
Eddie:
In the link I gave, they did not talk about any type of supernova.
I have also seen the life course of these stars, but I assume that not all stages create energetic radiation of the type observed.
When I read an article by researchers who delved into the subject and formulated a conclusion - my initial tendency - when I don't understand how they reached their conclusion - is to check what I didn't understand and what they didn't understand.
I have not the slightest doubt that in the case before us these are researchers who knew what a supernova was.
Original article in commenter 8's message
Read the original article from response 5 the best, without errors by the translator Yael
As shown by commenter 5
Essential errors, read the source
Michael Rothschild,
You are right, the supernova 1987A indicated in the link you provided is relatively new, so we cannot know how long it will take for its final decay.
But let's take for example a type 2 supernova (that is, in a massive star with a mass of at least 9 solar masses): the cessation of nuclear fusion due to the depletion of the hydrogen stock causes the star to collapse, emitting enormous energy. Here begins the process of fusion of the helium created earlier in the hydrogen fusion process. The helium fusion products are broken down in turn in new reactions that are getting shorter and shorter, but - all these processes, in particular the time periods between explosions - may take millions of years, until a neutron star is formed (or a black hole, when the mass in the last explosion is large enough).
If the above understanding is correct, the evidence against quantum gravity theories is provided, in my opinion.
Eddie:
There are never absolutes but:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980424a.html
I didn't quite understand the evidence against quantum gravity theories.
Suppose the more energetic (violet) photon was emitted at time (1)t which is the peak of the explosion. Let's assume that the less energetic photon (the yellow one) came out at time (2)t which is a long time after the explosion (there are supernovae whose process of collapsing into a neutron star may sometimes be measured over long periods of time) and is one of a huge number of less energetic photons that were emitted over a very long period of time.
Given the data of the event, it is possible that the speed of (1)t was indeed slowed due to its high energy, and it arrived at the reception system of the Fermi telescope in conjunction with one of a huge number of low-energy photons that were emitted over a long period of time.
If this is the case - and apparently it may indeed be the case - the evidence against the theories of quantum gravity does not exist, and in any case it is not decisive.
I would be happy to receive a clarifying opinion on the matter.
I believe that this is known by two satellites on opposite (polar) sides of the Earth.
Also, according to the wave form of the photon, it is possible to get information about the composition of the material of the emitting star.
Unfortunately, I only heard about it on a popular science level.
Maybe this only concerns energy particles?
They are not affected by matter but by other energy, such as gravity.
The link
http://www.sciencedaily.com/releases/2009/10/091028153447.htm
1+ for how do you know they are from the same source.
1+ for how do you know the time of their departure.
It would be nice if they added a link to the article in the article.
For those who are a little more interested:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08574.html
Maybe the Stringians will win in the end...
scribal error correction:
"Which is more likely to be due to the process of the gamma radiation burst, than in confirmation Einstein's ideas."
Instead of "in confirmation" there should be "refutation".
In relation to the questions raised - I agree with Ehud's opinion and add that apparently - if they detected a burst of gamma rays - they detected much more than two photons and probably also much more than one pair of photons, and they all arrived from the same point in space at more or less the same time.
I agree with the questions raised by my predecessors.
The uncertainty is too great.
Another possibility for the difference - isn't it possible that one of the photons traveled a longer path of 270,000 km, and its path curved in space?
Good Day
Sabdarmish Yehuda
I'm not an astrophysicist, but the photons coming from the gamma ray burst process are extremely energetic and cannot be found emitted from stars. In addition, any source at such a distance is a point source.
Very interested in the answers to Mr. Point's questions. Likewise, if the flash took 2 seconds, how can it be known that the two photons that have a difference of a little less than a second left the focus at exactly the same time?
Greetings friends,
Ami Bachar
A very significant result!
several questions:
How can you identify that the 2 photons are from the same source? How is it possible to identify the source with only 2 photons? Related to the previous one, how do you know how much time has passed since they were ejected?